HW 15 - johnson (mjj622) HW 15 Coker (56625) 1 This...

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Unformatted text preview: johnson (mjj622) HW 15 Coker (56625) 1 This print-out should have 17 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. This assignment covers the first chapter on wave motion, Ch. 16, which emphasizes trans- verse waves, the wave equation, wave power, reflection, superposition, standing waves and group speed. 001 10.0 points A transverse wave on a very long string is described by y ( x, t ) = (2 cm) sin bracketleftbig( 1 . 6 m- 1 ) x- ( 50 s- 1 ) t bracketrightbig What is the acceleration of the point at x = 0 at t = 3 4 seconds? 1. 50 m/s 2 2.- 10 cm/s 2 3.- 200 cm/s 2 4.- 50 m/s 2 correct 5. 2 cm/s 2 6. Zero; this is a standing wave. 7. 200 cm/s 2 8.- 62 . 5 cm/s 2 9. 10 cm/s 2 10. 1.6 m/s 2 Explanation: For y ( x, t ) = A sin( k x- t ), the accelera- tion of any point on the string is a y ( x, t ) = 2 y t 2 =- A 2 sin ( k x- t ) . sin(- ) =- sin , so at x = 0 a y (0 , t ) =- A 2 sin (- t ) = A 2 sin ( t ) , and for t = 3 4 , a y = (2 cm) ( 50 s- 1 ) 2 sin bracketleftbigg ( 50 s- 1 ) parenleftbigg 3 4 s parenrightbiggbracketrightbigg = ( 5000 cm / s 2 ) sin parenleftbigg 75 2 parenrightbigg = ( 5000 cm / s 2 ) sin parenleftbigg 36 + 3 2 parenrightbigg = ( 5000 cm / s 2 ) sin parenleftbigg 3 2 parenrightbigg = ( 5000 cm / s 2 ) (- 1) 1 m 100 cm =- 50 m / s 2 . 002 10.0 points A harmonic wave y = A sin[ k x- t- ] , where A = 1 m, k has units of m- 1 , has units of s- 1 , and has units of radians, is plotted in the diagram below. +1- 1 A (meters) x (meters) 2 4 6 At the time t = 0 Which wave function corresponds best to the diagram? 1. y = A sin bracketleftbigg parenleftbigg 2 15 m parenrightbigg x- t- parenleftbigg 1 3 parenrightbiggbracketrightbigg 2. y = A sin bracketleftbigg parenleftbigg 2 15 m parenrightbigg x- t- parenleftbigg 5 3 parenrightbiggbracketrightbigg 3. y = A sin bracketleftbigg parenleftbigg 2 9 m parenrightbigg x- t- parenleftbigg 5 3 parenrightbiggbracketrightbigg 4. y = A sin bracketleftbigg parenleftbigg 2 9 m parenrightbigg x- t- parenleftbigg 4 3 parenrightbiggbracketrightbigg johnson (mjj622) HW 15 Coker (56625) 2 5. y = A sin bracketleftbiggparenleftbigg 2 3 m parenrightbigg x- t- parenleftbigg 2 3 parenrightbiggbracketrightbigg 6. y = A sin bracketleftbiggparenleftbigg 2 15 m parenrightbigg x- t- parenleftbigg 2 3 parenrightbiggbracketrightbigg 7. y = A sin bracketleftbiggparenleftbigg 2 3 m parenrightbigg x- t- parenleftbigg 1 3 parenrightbiggbracketrightbigg 8. y = A sin bracketleftbiggparenleftbigg 2 9 m parenrightbigg x- t- parenleftbigg 1 3 parenrightbiggbracketrightbigg 9. y = A sin bracketleftbiggparenleftbigg 2 3 m parenrightbigg x- t- parenleftbigg 5 3 parenrightbiggbracketrightbigg 10. y = A sin bracketleftbiggparenleftbigg 2 3 m parenrightbigg x- t- parenleftbigg 4...
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This note was uploaded on 02/10/2011 for the course PHY 303K taught by Professor Turner during the Fall '08 term at University of Texas at Austin.

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HW 15 - johnson (mjj622) HW 15 Coker (56625) 1 This...

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